Xi'an Jiaotong University

About: Xi'an Jiaotong University is a education organization based out in Xi'an, China. It is known for research contribution in the topics: Heat transfer & Dielectric. The organization has 85440 authors who have published 99682 publications receiving 1579683 citations. The organization is also known as: '''Xi'an Jiaotong University''' & Xi'an Jiao Tong University.

Fast Fixed-time Nonsingular Terminal Sliding Mode Control and its Application to Chaos Suppression in Power System

Abstract: This brief presents a novel control scheme to achieve fast fixed-time system stabilization. Based on fixed-time stability theory, a novel fixed-time stable system is presented. Using the proposed fixed-time stable system, a fast fixed-time nonsingular terminal sliding mode control method is derived. Our control scheme achieves system stabilization within bounded time independent of the initial condition and has an advantage in convergence rate over the existing result of the fixed-time stable control method. The proposed control strategy is applied to suppress chaotic oscillation in power systems, and its effectiveness as well as superiority is verified through numerical simulation. The proposed control strategy can be applied to address the control and synchronization problem for other complex systems.

Aging behavior in single-domain Mn-doped BaTiO 3 crystals: Implication for a unified microscopic explanation of ferroelectric aging

Abstract: The change of ferroelectric, dielectric, and piezoelectric properties with time, the ferroelectric aging phenomena, has been observed in most ferroelectrics. Phenomenologically, aging can be attributed to the gradual stabilization of ferroelectric domains by defects, but the microscopic origin of the domain stabilization has remained controversial. It is unclear whether the domain stabilization is a boundary effect (caused by domain-wall-pinning) or a volume effect (stabilization of the whole domain). In the present paper, we made a single-domain (domain-wall-free) Mn-doped ${\mathrm{BaTiO}}_{3}$ single crystal and studied the aging behavior of its hysteresis loop. We found that after aging, the single-domain sample shows a significant increase in the coercive field, clearly indicating a strong stabilization of the single domain. Furthermore, the sample exhibits an abnormal double hysteresis loop, which corresponds to an interesting reversible domain switching process. These are direct evidence for the stabilization of single domain by aging. Our results preclude any explanation by the domain-wall-pinning effect and strongly suggest that the volume effect is the governing mechanism for the aging in hysteresis loop. We further show that the microscopic origin of the volume effect comes naturally from a general symmetry-conforming property of point defects. Such a microscopic mechanism can explain not only the aging in hysteresis loop (large signal aging) but also the aging in dielectric and piezoelectric constants (small signal aging), thus providing a unified microscopic explanation for all kinds of ferroelectric aging.

High permittivity and low loss microwave dielectrics suitable for 5G resonators and low temperature co-fired ceramic architecture

Abstract: Bi2(Li0.5Ta1.5)O7 + xBi2O3 (x = 0, 0.01 and 0.02) ceramics were prepared using a solid state reaction method. All compositions were crystallized in a single Bi2(Li0.5Ta1.5)O7 phase without secondary peaks in X-ray diffraction patterns. Bi2(Li0.5Ta1.5)O7 ceramics were densified at 1025 °C with a permittivity (er) of ∼ 65.1, Qf ∼ 15 500 GHz (Q ∼ microwave quality factor; f ∼ resonant frequency; 16 780 GHz when annealed in O2) and the temperature coefficient of resonant frequency (TCF) was ∼ −17.5 ppm °C−1. The sintering temperature was lowered to ∼920 °C by the addition of 2 mol% excess Bi2O3 (er ∼ 64.1, a Qf ∼ 11 200 GHz/11 650 GHz when annealed in O2 and at a TCF of ∼ −19 ppm °C−1) with compositions chemically compatible with Ag electrodes. Bi2(Li0.5Ta1.5)O7 + xBi2O3 are ideal for application as dielectric resonators in 5G mobile base station technology for which ceramics with 60 < er < 70, high Qf and close to zero TCF are commercially unavailable. They may additionally prove to be useful as high er and high Qf materials in low temperature co-fired ceramic (LTCC) technology.

Maximum Correntropy Kalman Filter

Abstract: Traditional Kalman filter (KF) is derived under the well-known minimum mean square error (MMSE) criterion, which is optimal under Gaussian assumption. However, when the signals are non-Gaussian, especially when the system is disturbed by some heavy-tailed impulsive noises, the performance of KF will deteriorate seriously. To improve the robustness of KF against impulsive noises, we propose in this work a new Kalman filter, called the maximum correntropy Kalman filter (MCKF), which adopts the robust maximum correntropy criterion (MCC) as the optimality criterion, instead of using the MMSE. Similar to the traditional KF, the state mean and covariance matrix propagation equations are used to give prior estimations of the state and covariance matrix in MCKF. A novel fixed-point algorithm is then used to update the posterior estimations. A sufficient condition that guarantees the convergence of the fixed-point algorithm is given. Illustration examples are presented to demonstrate the effectiveness and robustness of the new algorithm.